Thomaston is a town in Litchfield County, Connecticut, United States. The town is part of the Naugatuck Valley Planning Region. The population was 7,442 at the 2020 census. The urban center of the town is the Thomaston census-designated place, with a population of 1,928 at the 2020 census.

Litchfield County is in northwestern Connecticut, United States. As of the 2020 census, the population was 185,186. The county was named after Lichfield, in England. Litchfield County has the lowest population density of any county in Connecticut and is the state's largest county by area.